Imaging system having a liquid crystal element for selectively deflecting a beam path to vary the focal length thereof

Abstract

An imaging system for imaging an object onto an image sensor, and which has a front side facing the object and a rear side facing away from the object, the rear side being arranged behind the front side as viewed from the object. Furthermore, the imaging system has a light entrance device at the front side through which light coming from the object can enter into the imaging system. In this case, the light traverses the beam path between object and image sensor. At least one first and one second optical element are likewise present and are arranged at the rear side in such a way that they can influence the beam path. The light entrance device has an electrically switchable liquid crystal element which deflects the beam path at at least one first angle and a second angle which is different from the first angle depending on the electrical switching state. A discretely switchable focal length change is realized by this electrically effected change in the beam path.

The invention claimed is: 
     
       1. A variable focal length imaging system for imaging an object onto an image sensor, wherein the imaging system comprises:
 a) a front side facing the object; 
 b) a rear side facing away from the object, said rear side being arranged behind the front side as viewed from the object; 
 c) a light entrance device at the front side through which light coming from the object can enter into the imaging system; 
 d) at least one first and one second optical element which are arranged at the rear side in such a way that they can influence the focal length of the beam path within the imaging system; and 
 d1) an image sensor upon which light from the object passing through the entrance device and along the beam path is imaged; 
 characterized 
 e) in that the light entrance device has an electrically switchable liquid crystal element for selectively deflecting the beam path at at least one first angle and a second angle which is different from the at least one first angle, depending on the electrical switching state; 
 f) wherein the selected beam path impinges on the first optical element at the rear side at the at least one first angle, or on the second optical element at the rear side at the second angle; 
 g1) wherein when the beam path impinges on the first optical element at the rear side of the imaging system at the at least one first angle, at least a first focal length of the imaging system is obtained, and 
 g2) wherein when the beam path impinges on the second optical element at the rear side of the imaging system at the second angle, a second focal length different from the at least one first focal length of the imaging system is obtained. 
 
     
     
       2. A variable focal length imaging system as recited in  claim 1 ,
 characterized 
 
       in that a periodic grating of regions of a liquid crystal with ordered alignment of liquid crystal molecules can be formed in the liquid crystal element of the light entrance device by an electrical driving arrangement. 
     
     
       3. A variable focal length imaging system as recited in  claim 2 ,
 characterized 
 
       in that the electrical driving arrangement is embodied in such a way that it can form gratings of regions of the liquid crystal with ordered alignment of the liquid crystal molecules with different grating periods by respectively different driving in the liquid crystal element. 
     
     
       4. A variable focal length imaging system as recited in  claim 3 ,
 characterized 
 
       in that the light entrance device has a lens and a liquid crystal element. 
     
     
       5. A variable focal length imaging system as recited in  claim 3 ,
 characterized 
 
       in that the light entrance device has a Fresnel element and a liquid crystal element. 
     
     
       6. A variable focal length imaging system as recited in  claim 3 ,
 characterized 
 
       in that the light entrance device has a computer generated hologram and a liquid crystal element. 
     
     
       7. A variable focal length imaging system as recited in  claim 2 ,
 characterized 
 
       in that the light entrance device has a lens and a liquid crystal element. 
     
     
       8. A variable focal length imaging system as recited in  claim 2 ,
 characterized 
 
       in that the light entrance device has a Fresnel element and a liquid crystal element. 
     
     
       9. A variable focal length imaging system as recited in  claim 2 ,
 characterized 
 
       in that the light entrance device has a computer generated hologram and a liquid crystal element. 
     
     
       10. A variable focal length imaging system as recited in  claim 1 ,
 characterized 
 
       in that the light entrance device has a lens and a liquid crystal element. 
     
     
       11. A variable focal length imaging system as recited in  claim 1 ,
 characterized 
 
       in that the light entrance device has a Fresnel element and a liquid crystal element. 
     
     
       12. A variable focal length imaging system as recited in  claim 1 ,
 characterized 
 
       in that the light entrance device has a computer generated hologram and a liquid crystal element.